The control of the movement of sand and gravel into a wellbore has been the subject of much attention in the oil production industry. The introduction of sand or gravel into the wellbore commonly occurs under certain well conditions. The introduction of these materials into the well commonly causes problems including plugged formations or well tubing and erosion of tubing and equipment. There have therefore been numerous attempts to prevent the introduction of sand and gravel into the production stream.
One method of sand-control is the use of sand-control screen jackets to exclude sand from the production stream. The use of a radially expandable sand-control screen jacket includes causing the radial expansion of a screen jacket, and often base pipe, usually by drawing a mechanical expansion tool through the screen. There are several problems attendant with the apparatus and methods known in the art, some of which are enumerated below.
Expansion tools are typically in the form of a rigid mandrel introduced into the tubular to be expanded. The mandrel is dragged or pushed through the tubular, causing radial expansion by the application of brute force. The tubular itself is typically a corrosion resistant and structurally strong assembly of metal alloy. As a result, the expansion tool is subject to significant wear due to friction. There is therefore a need for a wear-resistant expansion tool.
Many expansion tools known in the art are of a fixed diameter. Commonly, the fixed-diameter expansion tool is introduced into the wellbore and positioned downhole, below the targeted production zone of the formation. The expandable tubular is then positioned adjacent to the targeted production zone, above the expansion tool, which is then drawn through the tubular to cause radial expansion. In such an operation, the fixed diameter of the expansion tool is required to be approximately equal to the desired size of the expanded tubular. This requirement often presents difficulties in positioning the tool. A few radially expandable expansion tools are known in the art, designed for introduction into the wellbore in a contracted state, then expanded for use. However, these attempted solutions are not completely satisfactory in structure having disadvantages in terms of manufacturing and operational complexity and strength. There is therefore a need for a new flexible expansion tool improving upon the art.
Further problems characteristic of downhole tubular expansion known in the art include: tearing of the tubular from over-expansion; under-expansion resulting in lack of contact between the expanded tubular and the wall of the borehole; and/or packing materials; and the expansion tool becoming lodged in the borehole. A related problem inherent in known apparatus and methods lies in lack of knowledge concerning whether over-expansion or under-expansion have occurred, necessitating additional trips downhole. Thus, there is a need for expansion tools and methods providing data-gathering and adjustable expansion capabilities according to downhole conditions.
In addition to the problems with mandrel surface wear mentioned above, there inheres the problem of seal wear. Commonly, a relatively fluid-tight seal is provided between an expansion tool and expandable tubular. Typically, such seals are made from an elastomeric material and/or mechanical seal elements, and are subject to wear due to contact with the expandable tubular. There is therefore a need for an expansion tool having a seal with wear-resistant properties.
Often the walls of a wellbore can become packed or “skinned” during drilling. Flow resistance at the wall of the hole, or “skin factor” must often be reduced before a sand-control screen assembly is installed in the formation. It is known in the art to reduce skin factor by washing the wellbore with a fluid selected for well and formation conditions. The washing is typically performed in a trip downhole separate from the one or more trips needed for installing and expanding a screen jacket assembly. Each trip downhole requires additional time and expense. There is a need to provide for washing of the borehole ahead of the expanding tubular during an expansion procedure.
Downhole tubular expansion systems known in the art often require one or more surface connections to facilitate powering or controlling expansion apparatus or methods. Surface connections often pose problems associated with the need to pass restrictions in borehole diameter or direction. There is therefore a need for downhole expansion tools and methods requiring no physical connection to the surface.